1. Field of the Invention
This invention relates to an outer lead bonding head and a bonding method thereof and, more particularly, to means for thermally press-bonding outer leads of semiconductor chips manufactured by a TAB (Tape Automated Bonding) method on a circuit board.
2. Description of the Prior Art
The TAB method is known to manufacture semiconductor chips by mounting the semiconductors on a film carrier made of a synthetic resin film and punching the film carrier.
The semiconductor chip manufactured as described above has outer leads formed by punching the film carrier as above, and it is generally called "an outer lead bonding" to bond the outer leads to electrodes formed on a circuit board.
Since the outer lead is extrafine, narrow at its pitch, and formed of extremely thin synthetic resin, the body of the lead is very weak, and it is remarkably difficult to accurately bring and bond the outer lead to the extrafine electrode formed on the circuit board.
A solder to be the material of the electrodes has melting and solidifying temperature characteristics, though depending upon sorts of the solders. It is generally desirable to gradually heat the solder up to 160.degree. to 180.degree. C., to then rapidly heat it to 220.degree. C. or higher to melt it, to then gradually cool it to solidify it. Since the outer lead is extrafine and extremely thin and formed of the synthetic resin such as polyimide, its quality is changed if it is rapidly heated to a high temperature not to be preferable and hence it should be gradually heated. As described above, since the bonding conditions of the outer lead are extremely severe, outer lead bonding technique is not yet established at present.